Field of the Invention and Related Art Statement
The present invention relates to an apparatus for controlling fluid pressure such as air pressure and oil pressure in a manifold type electromagnetic valve system having a plurality of electromagnetic valves.
In a fluid control system using a plurality of electromagnetic valves for controlling air pressure and oil pressure, respective electromagnetic valves and driving devices or controlling devices are connected to each other by means very complicated conduits. In order to simplify the connecting operation as well as to reduce a required space, there is some times used a manifold type electromagnetic valve system including a number of electromagnetic valves arranged on a common manifold base. In general, respective electromagnetic valves of the manifold type electromagnetic valve system are controlled by making on and off electric currents to solenoids of the electromagnetic valves. In the known manifold type electromagnetic valve system, the on and off operations of the solenoids are effected by controlling the driving power to the solenoids. That is to say, when the driving power is not supplied to a solenoid of an electromagnetic valve, the electromagnetic valve is closed or opened.
Therefore, to respective electromagnetic valves there have to connect two electric wires for conducting the driving power to the electromagnetic valves of single solenoid type arranged on the manifold base, there are arranged twenty electric wires, and when ten electromagnetic valves of double solenoid type are arranged, there have to be provided forty electric wires. In this manner, a quite large number of electric wires have to be connected to the manifold type electromagnetic valve system. This wiring operation requires very high cost and a large space for arranging a large bundle of electric wires. Moreover, when malfunction occurs due to the breakage or defects in contact, it is difficult to find positions of defects, so that it takes a quite long time until the manifold type electromagnetic valve system is repaired.
In order to avoid such a disadvantage there has been proposed a system in which the on-off control signals for respective electromagnetic valves are converted into a serial signal which is supplied via a single signal wire to the manifold and the driving power for the solenoids is supplied via a pair of power wires. In this case, to the manifold there are connected only three electric wires, two wires for the power supply and one wire for the control signal.
In the known system explained above, the serial control signal is reconverted into parallel control signals and these control signals are parallelly supplied to respective solenoids via respective control signal wires. Therefore, there must be arranged a plurality pairs of control signal wires the number of which is equal to that of the electromagnetic valves. Moreover, there must be arranged a serial-parallel converter and I/O ports for allotting the parallel control signals to respective electromagnetic valves. This results in that the manifold becomes large in size, so that the above mentioned solution could be hardly applied to the small size electromagnetic valve system. Further, since the wiring is complicated, there might occur breakage and poor connection of the wires and it is still difficult to find causes of malfunction so that it takes rather long time period until the manifold type electromagnetic system is repaired.
As explained above, the known solution requires rather complicated operation for arranging the serial-parallel converter on the manifold, and the effect could not be attained to an expected extent. Moreover, when it is required to provide another manifold system being coupled with the manifold system, it is necessary to provide transmitter unit and receiver unit for transmitting the control signal between these manifold systems. This results in that the whole system becomes further large in size.